Craig Sailor sent me this link to a paper in Nature that argues for a correlation between the gradual emergence of a certain kind of stone tool and the emergence of language. As Caig put it in his note to me:
"They suggest a causal relationship: the skills required to create the tools in question are complex enough that verbal instruction was significantly more effective than imitation (which they support with experimental evidence), meaning the gene(s) responsible for communication were preferentially selected for in the environment, leading to the general evolution of language."
They actually contrast five kinds of "transmission" mechanisms. Goring form the least interactive to the most they consider (i) Reverse engineering (subject given stone and tries to figure out how it was made) (ii) imitation/emulation (subjects watches someone make the stone and tries to copy this), (iii) basic teaching (proficient maker guides learner but no physical interaction), (iv) gestural teaching (teacher molds gestures of learner on stone) and (v) verbal teaching (teacher instructs learner by talking). The results of the experiment are that one finds better and better information transmission as one moves from (i) through to (v). In other words, as regards EVOLANG concerns, providing instruction via talking really helps. The suggestion is that "tool making created a continuous selective gradient from observational learning to much more complex verbal teaching…the more complex communication allowed the stable and rapid transmission of increasingly complex technologies, which in turn generate selection for even more complex communication and cognition, and so forth (5)." As the authors note (there are 12 of them). Their results place "little necessary constraint on when teaching and language may have evolved…" though they wish to suggest that this evo pressure of the indicated cline started having some effect at least 2.5 mya.
Some comments: It's pretty clear that the authors want to say something here about the evolution of our NL capacities (indeed, this is what made the results popular science newsworthy (see here)). However, so far as I can tell they do not isolate what specific linguistic features are required to juice the tool building transmission system. One can imagine a very limited "language" that would suffice (e.g. do this, like this, etc) to produce good tools and tool making instructions. And if this suffices to get good tool making and good tool making teaching then it is unclear what explanatory mileage one can get form this experiment. Said another way, the "proto-language" gestured to above (which strikes me as quite possibly sufficient for the tool making purposes discussed) is a very far cry from Natural Languages. And though, I am willing to grant that the more complex the language structure (both wrt word meaning and the combinatorics) the more information one can transmit, and the greater the complexity of the transmittable information the more complex the teaching that it can support, I do not see how this explains the emergence of FLs with the characteristics found in NLs. Or, to put this more charitably, I do not see that languages with the two basic features that we have discussed (here and here) are necessary for making tools. Note that I have no trouble seeing how the emergence of more and more complex linguistic systems can support more and more sophisticated teaching, but that does not support the causal direction of interest. The causal direction needs to be from tools to language not from language to tools.
Let me note two points: First, that unlike much of what passes for EVOLANG this work aims to give an account of how linguistic capacity evolved. The idea is that it piggy backs on selective advantage of tool making. This is good: it's heart is in the right place. Unfortunately, second, the paper is actually a nice example of the failings of much of the EVOLANG literature that I have looked at in that it never actually specifies what it takes to be the necessary features of languages required for the task at hand. Would the capacity to form simple NVN strings suffice? Would words that adhered to RD suffice (btw, I can't see why not on both counts)? Do we need unbounded hierarchically recursive structures to get flint tool making off the ground? Who knows? The problem is not that the paper doesn't address this issue, but it doesn't even recognize its relevance.
Let me end by stating again what someone like me (and I suspect you too) want out of an EVOLANG account: how did our linguistic capacity arise? Which one is that? Well, for starters, where did the linguistic capacity with the two key features Chomsky discussed in the above linked to articles come from? Isolate the features of language without which tool creating transmission information is impossible. That's a first step. The second is to show that the causality is from tools to language capacity, rather than the other way around. So, sure there is a correlation: more complex tools goes with more complex language, but more complex everything goes with more complex language. So big deal.
Let me say this another way: the paper, taken at face value, suggests that some kind of communication system would have been useful in making the flint tool discussed. However, as noted this does not imply that on had an NL like ours earlier than 75-50 kya. It only says that it would have been useful. But quite possibly (likely) a more limited communication system with properties quite unlike those found in our NLs would have been just as useful for this task. Nor is there any reason given why having such a more primitive system is a causal precondition for having ours. And therefore the relevance of the results completely escapes me. Here is yet another case where not describing the properties whose evolution you want to explain has led to a whole bunch of time intensive hard work being done with no obvious gain in insight. In sum, this looks like another case of those things not worth doing are not worth doing well.